Imagine an underground chamber like a cave, with a long entrance open to the daylight and as wide as the cave. In this chamber are men who have been prisoners since they were children, their legs and their necks being so fastened that they can only look straight ahead of them and cannot turn their heads. Some way off, behind and higher up, a fire is burning, and between the fire and the prisoners and above them runs a road, in front of which a curtainwall has been built, like the screen at puppet shows between the operators and their audience. . . . Our prisoners could [not] see anything . . . except for the shadows thrown by the fire on the wall of the cave opposite them.3

The ancient Greek philosopher Plato wrote these words about twenty-four hundred...